Lubricating compositions with enhanced deposit performance

ABSTRACT

A lubricant composition includes a lubricating base oil, a controlled release friction modifier, a dispersant, a viscosity modifier and a cleanliness booster. The controlled release friction modifier is an ashless, dispersant-stabilized, borated controlled release friction modifier including an ionic tetrahedral borate compound including a cation and a tetrahedral borate anion, wherein the tetrahedral borate anion includes a boron atom having two bidentate di-oxo ligands of C 18  tartrimide.

This nonprovisional application claims priority to U.S. Provisional Application No. 62/535,527, which was filed on Jul. 21, 2017, and is herein incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a lubricant composition, in particular, a lubricant composition, suitable for use in, for example, internal combustion engines, which reduces deposit formation and friction in an engine.

Description of the Background Art

Engine oils are formulated for the purpose of reducing friction in the engine, engine cleanliness (e.g., deposit control), control of wear, corrosion and rust in the engine. To accomplish this goal, engine oils contain numerous and various additives including friction modifiers, detergents, dispersants, viscosity modifiers and antioxidants.

Of significant concern is the reduction of friction in engines so as to improve fuel economy necessitating the use of lower viscosity lubricating base stocks while also meeting the competing requirements of maintaining sufficiently high lubricating oil film thickness at high operating temperature to avoid incidental breakdown of the oil film under boundary conditions while still maintaining low wear over a wide range of temperatures.

Traditionally, fuel economy favors lower viscosity engine oils and the use of friction modifying additives. Fuel economy, often measured in operating engine tests, is only one of many performance needs of modern engine oil. Other performance needs include, for example, oxidation stability of the lubricant over time, deposit formation on internal engine surfaces and a variety of physical and chemical tests needed to ensure the oil will be suitable in an engine. Because there are many requirements, the chemistry used to formulate engine oils is complex. Often a particular additive that can improve one aspect of a lubricant's performance works against the performance enabled by other additives.

Current well known fuel economy additives include various oil-soluble compounds of molybdenum as well as NOCH (nitrogen, oxygen-containing chemistries). The highest performing lubricants usually entail the use of base oils that are highly paraffinic. Such base oils would include API Group IV polyalphaolefin (PAO) base oils, API Group III base oils such as gas-to-liquid base oils and potentially even highly saturated Group II base oils. Such oils are highly non-polar and, as a result, have a limited amount of solubility for polar additives. Additionally, the use of highly paraffinic base oils can increase the amount of unwanted deposit formation.

Friction modifiers, which are among the additives used in lubricant compositions, are used to improve the composition's ability to reduce friction. Among the friction modifiers that can be used in a lubricant composition are borated friction modifiers. Documents disclosing conventional borated friction modifiers include U.S. Pat. No. 4,522,734A disclosing borated long-chain (C10-20) epoxides, EP 0036708A1 disclosing borated fatty acid esters of glycerol, U.S. Pat. No. 5,759,965A disclosing borated alkoxylated fatty amines, US 2009/0005276A1 disclosing borated polyalkene succinimides, WO 2007005423A2 disclosing a reaction product of C8-20 fatty acids with dialkanolamines and boric acid, CA 1336830C disclosing borated hydroxyl ether amines and U.S. Pat. No. 4,522,629A disclosing borated phosphonates. While these documents disclose borated friction modifiers, there still exists a need for lubricant compositions including borated friction modifiers, which better facilitate improvements in the necessary benefits described above.

Specifically, most fuel economy additives, including the friction modifiers detailed above, are highly polar and, as such, are challenged to remain soluble in the lubricating oil. With limited solubility and availability of the additives, improvements in fuel economy are similarly limited. In addition, many of the additives degrade or are consumed in service with the result that fuel economy is more difficult to maintain for extended times. Additionally, conventional friction modifiers typically cause increased deposit formation as they have limited solubility and are rapidly oxidized in-service.

Known lubricant compositions for use as motor oils are described in documents such as U.S. Pat. No. 9,193,934B2, U.S. Pat. No. 9,163,196B2, US 2014/0045734A1, U.S. Pat. No. 9,175,241B2, US 2012/0283158A1 and US 2014/0107000A1. These documents describe compositions that have been formulated for clarity and stability. These documents, however, do not describe compositions that have been formulated to provide increased fuel economy while also reducing deposit formation and friction in an engine. Accordingly, there exists a need for improved lubricant compositions including additives that highly soluble and mitigate unwanted deposit formation, thus providing an increased cleanliness.

SUMMARY OF THE INVENTION

In view of the foregoing and other exemplary problems, drawbacks, and disadvantages of the conventional methods and compositions, an exemplary feature of the present invention is to improve fuel economy by providing a lubricating oil composition having an increased amount of friction modifier while also mitigating deposit formation through a combination of additives that include a synergistic use of dispersant, viscosity modifier and cleanliness booster.

In accordance with a first exemplary, non-limiting aspect of the present invention, a lubricant composition includes a lubricating base oil, a controlled release friction modifier (CRFM), a dispersant, a viscosity modifier and a cleanliness booster.

In accordance with a second exemplary, non-limiting aspect of the present invention, a lubricant composition includes 26-94% highly paraffinic base oil, 2%-8% CRFM, 1%-15% dispersant, 1%-15% viscosity modifier, 1%-10% detergent and 0.5%-3% cleanliness booster.

In accordance with a third exemplary, non-limiting aspect of the present invention, a lubricant composition includes a highly paraffinic lubricating base oil, an ashless CRFM including a dispersant-stabilized, borated CRFM comprising an ionic tetrahedral borate compound including a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are in cationic form (referred to herein as a dispersant-stabilized borated CRFM) an additional dispersant selected from a group consisting of succinimide, polyolefin amide alkeneamine, ethylene capped succinimide and borated polyisobutylsuccinimide-polyamine, a viscosity modifier comprising a hydrogenated isoprene star polymer and a cleanliness booster comprising an alkyl phenol ether polymer or polyisobutylene.

In accordance with a fourth exemplary, non-limiting aspect of the present invention, a lubricant composition consists of, or is formed only of, 10% polyalphaolefin base oil, 64.21% Group III base oil, 5% alkylated naphthalene co-baseoil, 4.99% of a package of supporting additives including antioxidants, detergents, antiwear, antifoam, inorganic friction modifiers and pour point depressants, 6.4% hydrogenated isoprene star polymer 7, 1% of a cleanliness booster, 0.74% borated PIBSA/PAM dispersant, 3.7% succinimide dispersant and 3.96% of an ashless, dispersant-stabilized borated CRFM.

Accordingly, the claimed invention includes a dispersant-stabilized, borated CRFM that provides a much larger amount of friction modifier in the lubricating oil composition, which results in improved overall fuel economy. Additionally, the CRFM is a low-ash composition, which reduces potential damage from ash to ash particulate filters.

Adding the above CRFM to a lubricating oil composition offers a number of challenges, including CRFM deposit formation. The composition of the present invention has surprisingly mitigated the formation of deposits from the CRFM by also including a combination of additives that include a synergistic use of dispersant, viscosity modifier and cleanliness booster. Thus, the present invention provides a lubricating oil composition that not only improves overall fuel economy but does so while meeting other performance specifications that require the VW TDi2 (CEC L-78-99).

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus, do not limit the present invention, and wherein:

FIG. 1 is a graph illustrating effects of CRFM on deposit merits; and

FIG. 2 is a graph illustrating deposit merits of lubricating oil compositions according to certain exemplary embodiments of the present invention.

DETAILED DESCRIPTION

Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the scope of the invention. Additionally, well-known elements of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The present invention is directed to a lubricant composition suitable for use as an engine oil, the usage of which results in improved fuel economy throughout the time that the composition is used in an engine while also mitigating deposit formation through a combination of additives that include a synergistic use of dispersant, viscosity modifier and cleanliness booster. In some embodiments, the lubricant composition comprises a CRFM. Additionally, in some exemplary embodiments, the lubricant composition further comprises an American Petroleum Institute (API) Group III base stock, a polyalphaolefin (PAO) base stock, a dispersant, a viscosity modifier and a cleanliness booster. In some exemplary embodiments, the lubricant composition further comprises at least one of, a Group V co-base stock, an inorganic friction modifier, a dispersant, a detergent, as well as other lubricant composition additives.

Basestocks

In certain exemplary embodiments of the present invention, the lubricating composition includes API Group III base oils and/or API Group IV polyalphaolefin (PAO) base oils as base stock. In certain exemplary embodiments, the lubricant composition also includes API Group V base oil as a co-base stock.

A wide range of lubricating base oils is known in the art. Lubricating base oils are both natural oils and synthetic oils. Natural and synthetic oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using oil that has been previously used as feed stock.

Groups I, II, III, IV and V are broad categories of base oil stocks developed and defined by the American Petroleum Institute (API Publication 1509) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between 80 to less than 120 and contain greater than about 0.03% sulfur and less than 90% saturates. Group II base stocks have a viscosity index of between 80 to less than 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than or equal to 120 and contain less than or equal to 0.03% sulfur and greater than 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV Includes polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source; for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification; for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks, as well as synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters, i.e. Group IV and Group V oils are also well known base stock oils.

Synthetic oils include hydrocarbon oil such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks, the Group IV API base stocks, are a commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073, which are incorporated herein by reference in their entirety. Group IV oils, that is, the PAO base stocks have viscosity indices preferably greater than 125, more preferably greater than 135, still more preferably greater than 140.

The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatics can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C₆ up to about C₆₀ with a range of about C₈ to about C₄₀ often being preferred. A mixture of hydrocarbyl groups is often preferred. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to about 50 cSt are preferred, with viscosities of approximately 3.4 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols such as the neopentyl polyols; e.g., neopentyl glycol, trimethylol ethane, 2 methyl 2 propyl 1,3 propanediol, trimethylol propane, pentaerythritol and dipentaerythritol with alkanoic acids containing at least about 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acids, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Non-conventional or unconventional base stocks and/or base oils include one or a mixture of base stock(s) and/or base oil(s) derived from: (1) one or more Gas-to-Liquids (GTL) materials, as well as (2) hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oils derived from synthetic wax, natural wax or waxy feeds, mineral and/or non-mineral oil waxy feed stocks such as gas oils, slack waxes (derived from the solvent dewaxing of natural oils, mineral oils or synthetic oils; e.g., Fischer Tropsch feed stocks), natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, foots oil or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials recovered from coal liquefaction or shale oil, linear or branched hydrocarbyl compounds with carbon number of about 20 or greater, preferably about 30 or greater and mixtures of such base stocks and/or base oils.

Base oils for use in the formulated lubricating oils useful in the present invention are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

In accordance with certain exemplary embodiments of the present invention, the lubricating oil includes base oils (base stocks) of 75 wt % to 94 wt % of the total lubricating oil composition. In accordance with certain exemplary embodiments, the base oil includes a highly paraffinic base oil, chosen from a Group III oil or a polyalphaolefin base oil. The highly paraffinic base oil may include the Group III oil, the polyalphaolefin base oil or a combination of both. Preferably, the highly paraffinic base oil makes up 26 wt % to 94 wt %, and even more preferably, 47 wt % to 94 wt % of the total lubricating oil composition by weight. Furthermore, in certain exemplary embodiments of the invention, the base oil may also include a Group V base oil. The Group V base oil is preferably selected from ester and alkylated naphthalene. The Group V base oil may be present in an amount ranging from 0 wt % to 15 wt % of the total lubricating oil composition and, even more preferably, in an amount ranging from 0 wt % to 10 wt %. In certain preferable embodiments, the lubricating oil composition includes 5 wt % of Group V base oil.

Controlled Release Friction Modifier (CRFM)

In accordance with certain exemplary aspects of the present invention, the lubricating composition includes a CRFM. The CRFM is a dispersant-stabilized, borated CRFM comprising an ionic tetrahedral borate compound including a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimide compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are in cationic form. As used herein, the term “conventional ammonium substituted polyisobutenyl succinimide,” refers to an ammonium substituted polyisobutenyl succinimide made by the chorine-assisted process. Such a process is well known in the art. One such process includes grafting maleic anhydride to polyisobutenyl in the presence of chorine followed by reaction with a poly(amine) to form the imide.

In accordance with another aspect of the exemplary embodiment, the CRFM includes a reaction product of a trivalent boron compound, such as boric acid, with a tartaric acid and a linear C18 amine under conditions suitable to form an ionic tetrahedral borate compound. The ionic tetrahedral borate compound is combined with a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimide compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are converted to a cationic form.

The above described ionic tetrahedral borate compound can serve as a friction modifier, in a lubricating composition.

In one embodiment, the structure of the tetrahedral borate ion of the tetrahedral borate compound may be represented by the structure shown in Formula I:

where R3, R4 form a 5 membered nitrogen-containing heterocyclic ring substituted with a linear C18 group.

The cations in Formula I include one or more of a first ammonium cation including a conventional polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent of at least 750, and can be up to 2500, and a second ammonium cation is including a polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent of at least 750, and can be up to 2,500, having an N:CO ratio of 1.8. Such succinimides can be formed, for example, from high vinylidene polyisobutylene and maleic anhydride.

Total base number (TBN) is the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide (meq KOH), that is required to neutralize all basic constituents present in 1 gram of a sample of the lubricating oil. The TBN may be determined according to ASTM Standard D2896-11, “Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration” (2011), ASTM International, West Conshohocken, Pa., 2003 DOI: 10.1520/D2896-11 (hereinafter, “D2896”).

Specific examples of such amine and ammonium compounds include polyisobutylene derived succinimide dispersants wherein the polyisobutylene may be 1000 Mn and the succinimide amine is a polyethylenepolyamine (Mn 1700 g/mol).

A useful molar ratio of the tartaric acid, the trivalent boron compound, and counter ion charge used in forming the combination and/or reaction product is 2:1:1.

In an embodiment, the linear C₁₈ tartrimide compound is derived from tartaric acid. The tartaric acid used for preparing the tartrates of the invention can be commercially available, and it is likely to exist in one or more isomeric forms such as d-tartaric acid, l-tartaric acid, d,l-tartaric acid, or mesotartaric acid, often depending on the source (natural) or method of synthesis (from maleic acid). For example a racemic mixture of d-tartaric acid and l-tartaric acid is obtained from a catalyzed oxidation of maleic acid with hydrogen peroxide (with tungstic acid catalyst). These derivatives can also be prepared from functional equivalents to the diacid readily apparent to those skilled in the art, such as esters, acid chlorides, or anhydrides. The suitable amines will have the formula RNH₂ wherein R represents a hydrocarbyl group, typically of 6 to 26. Exemplary primary amines include n-hexylamine, n-octylamine (caprylylamine), n-decylamine, n-dodecylamine (laurylamine), n-tetradecylamine (myristylamine), n-pentadecylamine, n-hexadecylamine (palmitylamine), n-octadecylamine (stearylamine), and oleylamine.

Suitable trivalent boron compounds include borate esters of the general form B(OR)₃ where each R is 2-propylheptyl. In an embodiment, the counter ion is a basic component, such as a dispersant. The source of the counter ion may be an aminic dispersant. For solubilization in mineral oil, particular examples include polyisobutenyl succinimide and polyamine dispersants with a N:CO ratio of 1.8 and with a TBN of at least 50.

In an embodiment, the ionic borate compound is the reaction product of a tartrimide, a borate ester, and at least one basic component, such as two dispersants, to form a “boro-tartrimide” friction modifier. The ionic boron compound described herein is used to improve friction.

A problem with conventional friction modifiers, as noted above, is that the friction modifier is not sufficiently soluble, which leads to an insufficient amount of friction modifier being available during consumption of the lubricating oil and sludge (i.e., deposits) may form. The CRFM in accordance with certain exemplary embodiments of the present invention maintains sufficient friction modifier at the surface to provide lower friction lubricating oils while improving overall fuel economy. That is, the CRFM described herein raises the amount of friction modifier by using a tetra-valent boron chemistry to complex the friction modifier. This results in a much larger amount of friction modifier in the lubricating oil with resulting improvements to fuel economy. Also, it is know that ash can damage the particulate filter of an engine. High ash compositions (i.e., compositions with high amounts of detergent) are not desirable. The present CRFM is preferably a low ash CRFM.

In accordance with certain exemplary embodiments of the present invention, the CRFM is an ashless, dispersant-stabilized, borated friction modifier. Additionally, the lubricating oil composition may include an amount of CRFM in a range of 2 wt % to 8 wt %, and more preferably in a range of 3 wt % to 5 wt %, of the total lubricating oil composition. In certain specific preferred embodiments, the CRM is provided in an amount of 3.96 wt %.

Additives

As noted above, lubricating oils have several competing concerns (e.g., fuel economy, cleanliness, performance, etc.) that must be balanced. In order for the lubricating oil to meet all performance and cleanliness standards while also improving fuel economy with use of the above CRFM, the lubricating oil must also include other additives. For example, creating engine oil formulations incorporating the above CRFM can result in increased engine deposits from the CRFM. The present inventors have discovered that the deposits can be mitigated by providing a combination of additives along with the CRFM. Thus, by using the CRFM in addition to the combination of additives the lubricating oil composition according to the exemplary embodiments of the invention described herein is able to improve fuel economy without engine sludge (i.e., improved cleanliness). In accordance with certain exemplary embodiments of the invention, the combination of additives includes a dispersant, a viscosity modifier and a cleanliness booster, which together allow the lubricating oil to meet performance specifications containing the VW TDi2 deposit test.

The formulated lubricating oil useful in the present invention may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to dispersants, other detergents, corrosion inhibitors, rust inhibitors, metal deactivators, other anti-wear agents and/or extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, other friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0 89573 177 0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973).

Viscosity Modifier

Viscosity modifiers/improvers (also known as Viscosity Index modifiers, and VI improvers) increase the viscosity of the oil composition at elevated temperatures which increases film thickness, while having limited effect on viscosity at low temperatures.

Suitable viscosity improvers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,000,000, more typically about 20,000 to 500,000, and even more typically between about 50,000 and 200,000.

Examples of suitable viscosity improvers are polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity index improver. Another suitable viscosity index improver is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity index improvers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

In accordance with certain preferred embodiments of the present invention, the viscosity modifier includes hydrogenated isoprene star polymer 7. Hydrogenated isoprene star polymer 7 is a hydrogenated isoprene star polymer having a bimodal molecular weight distribution as defined by dynamic light scattering of a primary peak at 1004000 g/mol and a secondary peak at 143000 g/mol The amount of viscosity modifier may range from 1 wt % to 15 wt %, preferably 1 wt % to 8 wt %, and more preferably 1.8 wt % to 6.4 wt % based on active ingredient and depending on the specific viscosity modifier used.

Detergents

Detergents can include alkali and alkaline earth metal phenates, sulfonates, carboxylates, phosphonates, calcium phenates, calcium sulfonates, magnesium phenates, magnesium sulfonates, other related components (including borated detergents) and mixtures thereof. In accordance with certain exemplary embodiments of the invention, the detergent may be selected from highly overbased calcium salicylate, low base calcium salicylate, overbased magnesium sulfonate and neutral calcium sulfonate, and they can be present either individually or in combination with each other in an amount in the range of from 1 wt % to 10 wt %, preferably 1 wt % to 5 wt %, and even more preferably from 2.03 wt % to 3.8 wt % (active ingredient) based on the total weight of the formulated lubricating oil.

Dispersant

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain substituted alkenyl succinic compound, usually a substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid compounds are popular dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between alkenyl succinic anhydrides and amines. Molar ratios can vary depending on the amine or polyamine. For example, the molar ratio of alkenyl succinic anhydride to TEPA can vary from about 1:1 to about 5:1.

Succinate esters are formed by the condensation reaction between alkenyl succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of an alkenyl succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between alkenyl succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine.

The molecular weight of the alkenyl succinic anhydrides will typically range between 800 and 2,500. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid, and boron compounds such as borate esters or highly borated dispersants. The dispersants can be borated with from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500.

Typical high molecular weight aliphatic acid modified Mannich condensation products can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HN(R)₂ group-containing reactants.

Examples of high molecular weight alkyl-substituted hydroxyaromatic compounds are polypropylphenol, polybutylphenol, and other polyalkylphenols. These polyalkylphenols can be obtained by the alkylation, in the presence of an alkylating catalyst, such as BF₃, of phenol with high molecular weight polypropylene, polybutylene, and other polyalkylene compounds to give alkyl substituents on the benzene ring of phenol having an average 600-100,000 molecular weight.

Examples of HN(R)₂ group-containing reactants are alkylene polyamines, principally polyethylene polyamines. Other representative organic compounds containing at least one HN(R)₂ group suitable for use in the preparation of Mannich condensation products are well known and include the mono- and di-amino alkanes and their substituted analogs, e.g., ethylamine and diethanol amine; aromatic diamines, e.g., phenylene diamine, diamino naphthalenes; heterocyclic amines, e.g., morpholine, pyrrole, pyrrolidine, imidazole, imidazolidine, and piperidine; melamine and their substituted analogs.

Examples of alkylene polyamine reactants include ethylenediamine, diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, pentaethylene hexamine, hexaethylene heptaamine, heptaethylene octaamine, octaethylene nonaamine, nonaethylene decamine, and decaethylene undecamine and mixture of such amines having nitrogen contents corresponding to the alkylene polyamines, in the formula H₂N—(Z—NH—)_(n)H, mentioned before, Z is a divalent ethylene and n is 1 to 10 of the foregoing formula. Corresponding propylene polyamines such as propylene diamine and di-, tri-, tetra-, pentapropylene tri-, tetra-, penta- and hexaamines are also suitable reactants. The alkylene polyamines are usually obtained by the reaction of ammonia and dihalo alkanes, such as dichloro alkanes. Thus the alkylene polyamines obtained from the reaction of 2 to 11 moles of ammonia with 1 to 10 moles of dichloroalkanes having 2 to 6 carbon atoms and the chlorines on different carbons are suitable alkylene polyamine reactants.

Aldehyde reactants useful in the preparation of the high molecular products useful in this invention include the aliphatic aldehydes such as formaldehyde (also as paraformaldehyde and formalin), acetaldehyde and aldol (β-hydroxybutyraldehyde). Formaldehyde or a formaldehyde-yielding reactant is preferred.

Exemplary dispersants include borated and non-borated succinimides, including those derivatives from mono-succinim ides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000 or a mixture of such hydrocarbylene groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components.

In accordance with certain exemplary embodiments of the invention, the dispersant may preferably include succinimide, polyolefin amide alkeneamine, ethylene capped succinimide and borated polyisobutylsuccinimide-polyamine. The dispersant may be used in an amount of about 1 wt % to 15 wt %, preferably about 2 wt % to 12 wt %, more preferably about 4.44 wt % to 9.8 wt % based on the weight of the total lubricant composition.

Cleanliness Booster

The lubricating oil composition further includes a cleanliness booster. Cleanliness boosters refer to a broad class of commercially available components used to reduce hard carbonaceous deposits that form on the piston land and groove surfaces of diesel engines due to degradation of the base oil and oil additives under extremely high temperatures. Keeping an engine free of deposits is highly desirable as the deposits in an engine reduce effective heat transfer, contribute to friction, and change the highly engineered clearances of a modern engine which can result is wear. Cleanliness is difficult to achieve in a modern engine oil formulation due to limits placed on ash containing componentry (e.g., overbased detergents) which are used to prevent formation of deposits. These ash limits are in place to reduce blockage of diesel particulate filters and limit the amount of an overbased detergent that may be used in a given engine oil formulation. One method of overcoming this limit is through the use of ashless cleanliness boosters. Some of these materials which are commercially available include alkyl phenol ether polymers, polyisobutylene polymers and ashless detergent chemistries. These materials are typically used in a formulation in a range from 0.5-2.0 wt. % and provide a modest but consistent improvement in cleanliness, in particular in the VW PV1452 TDi-2 Deposit Test (CEC L-078-99) which is used in multiple ACEA and OEM claims. This cleanliness boost can range from 1-5 piston deposit merits in the VW PV1452 test depending on depending on specific chemistry selected, formulation, and treat rate. According to certain exemplary embodiments of the invention, the cleanliness booster may include alkyl phenol ether polymer, polyisobutylene or a combination thereof. The cleanliness booster may be used in an amount of about 0.5 wt % to 3 wt %, preferably about 0.5 wt % to 1.5 wt %, more preferably about 1 wt % based on the weight of the total lubricant composition.

Other Additives

As noted above, lubricating oils have several competing concerns (e.g., fuel economy, cleanliness, performance, etc.) that must be balanced. In order for the lubricating oil to meet all performance and cleanliness standards while also improving fuel economy with use of the above CRFM, the lubricating oil must also include other additives. In total, the amount of these other additives may range from 1 wt % to 8 wt % and preferably 2 wt % to 5 wt %.

The following other additives may be chosen from conventional friction modifiers, antiwear additives, pour point depressants, antioxidants, antifoam agents and seal swell additives.

Antioxidants

An anti-oxidant such as a phenolic, aminic, copper compound, organic sulfide, disulfide or polysulfide can also be present and is preferably present. Typical antioxidants include phenolic antioxidants, aminic antioxidants and oil-soluble copper complexes. The phenolic antioxidants include sulfurized and non-sulfurized phenolic antioxidants. The terms “phenolic type” or “phenolic antioxidant” used herein includes compounds having one or more than one hydroxyl group bound to an aromatic ring which may itself be mononuclear, e.g., benzyl, or poly-nuclear, e.g., naphthyl and spiro aromatic compounds. Thus “phenol type” includes phenol per se, catechol, resorcinol, hydroquinone, naphthol, etc., as well as alkyl or alkenyl and sulfurized alkyl or alkenyl derivatives thereof, and bisphenol type compounds including such bi-phenol compounds linked by alkylene bridges sulfuric bridges or oxygen bridges. Alkyl phenols include mono- and poly-alkyl or alkenyl phenols, the alkyl or alkenyl group containing from about 3-100 carbons, preferably 4 to 50 carbons and sulfurized derivatives thereof, the number of alkyl or alkenyl groups present in the aromatic ring ranging from 1 to up to the available unsatisfied valences of the aromatic ring remaining after counting the number of hydroxyl groups bound to the aromatic ring.

Generally, therefore, the phenolic anti-oxidant may be represented by the general formula:

(R)_(x)—Ar—(OH)_(y)

where Ar is selected from the group consisting of:

wherein R is a C₃-C₁₀₀ alkyl or alkenyl group, a sulfur substituted alkyl or alkenyl group, preferably a C₄-C₅₀ alkyl or alkenyl group or sulfur substituted alkyl or alkenyl group, more preferably C₃-C₁₀₀ alkyl or sulfur substituted alkyl group, most preferably a C₄-C₅₀ alkyl group, R^(g) is a C₁-C₁₀₀ alkylene or sulfur substituted alkylene group, preferably a C₂-C₅₀ alkylene or sulfur substituted alkylene group, more preferably a C₂-C₂ alkylene or sulfur substituted alkylene group, y is at least 1 to up to the available valences of Ar, x ranges from 0 to up to the available valances of Ar-y, z ranges from 1 to 10, n ranges from 0 to 20, and m is 0 to 4 and p is 0 or 1, preferably y ranges from 1 to 3, x ranges from 0 to 3, z ranges from 1 to 4 and n ranges from 0 to 5, and p is 0.

Preferred phenolic anti-oxidant compounds are the hindered phenolics and phenolic esters which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic anti-oxidants include the hindered phenols substituted with C₁+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; 2-methyl-6-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4 methyl phenol; 2,6-di-t-butyl-4-ethyl phenol; and 2,6-di-t-butyl 4 alkoxy phenol; and

Phenolic type anti-oxidants are well known in the lubricating industry and commercial examples such as Ethanox® 4710, Irganox® 1076, Irganox® L1035, Irganox® 1010, Irganox® L109, Irganox® L118, Irganox® L135 and the like are familiar to those skilled in the art. The above is presented only by way of exemplification, not limitation on the type of phenolic anti-oxidants which can be used.

The phenolic anti-oxidant can be employed in an amount in the range of about 0.1 to 3 wt %, preferably about 1 to 3 wt %, more preferably 1.5 to 3 wt % on an active ingredient basis.

Aromatic amine anti-oxidants include phenyl-α-naphthyl amine which is described by the following molecular structure:

wherein R^(z) is hydrogen or a C₁ to C₁₄ linear or C₃ to C₁₄ branched alkyl group, preferably C₁ to C₁₀ linear or C₃ to C₁₀ branched alkyl group, more preferably linear or branched C₆ to C₈ and n is an integer ranging from 1 to 5 preferably 1. A particular example is Irganox L06.

Other aromatic amine anti-oxidants include other alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(x)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to about 20 carbon atoms, and preferably contains from about 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines anti-oxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than about 14 carbon atoms. The general types of such other additional amine anti-oxidants which may be present include diphenylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more of such other additional aromatic amines may also be present. Polymeric amine antioxidants can also be used.

Another class of anti-oxidant used in lubricating oil compositions and which may also be present are oil-soluble copper compounds. Any oil-soluble suitable copper compound may be blended into the lubricating oil. Examples of suitable copper antioxidants include copper dihydrocarbyl thio- or dithio-phosphates and copper salts of carboxylic acid (naturally occurring or synthetic). Other suitable copper salts include copper dithiacarbamates, sulphonates, phenates, and acetylacetonates. Basic, neutral, or acidic copper Cu(I) and or Cu(II) salts derived from alkenyl succinic acids or anhydrides are known to be particularly useful.

Such anti-oxidants may be used individually or as mixtures of one or more types of anti-oxidants.

Pour Point Depressants

Conventional pour point depressants (also known as lube oil flow improvers) may also be present. Pour point depressant may be added to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include alkylated naphthalenes polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers.

Anti-Foam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers.

The types and quantities of performance additives used in combination with the instant invention in lubricant compositions are not limited by the examples shown herein as illustrations.

Examples

As noted above, creating engine oil compositions including a CRFM presented certain challenges to the present inventors. Particularly, the addition of a CRFM to the lubricating oil composition can result in unmanageable deposit formation from the CRFM.

FIG. 1 illustrates a graph of TDi2 piston deposit merits for initial CRFM formulations. The piston deposit merit is a cleanliness grade for an engine oil. A merit score of 65 indicates a passing grade with 70 indicating an exceptionally clean formulation. As is illustrated in FIG. 1, an initial lubricating oil (comparative example 2A), which did not include any CRFM, had a deposit merit score of 65. When CRFM was added to this initial oil, the deposit merit score drop significantly to 54 (comparative example 2B) and 50 (comparative example 2C), respectively. Thus, with merely adding CRFM to an existing engine oil, the deposit merit score dropped to well below passing. Similarly, another initial lubricating oil (comparative example 1A), which also did not include any CRFM, had a deposit score of 68, which is above passing. When a CRFM was added to this oil (comparative example 1B) the merit score dropped to approximately 65. In this case, while the merit score for 1B was still passing, the sole addition of CRFM to the existing engine oil had a detrimental effect on the deposit merit score, despite the fact that this example is a high (1.20 wt. %) sulfated ash formulation.

Table 1 below illustrates these two examples (Comparative Example 1A and Comparative Example 1B) which represent early, high ash formulations of engine oils. Comparative Example 1A did not include a CRFM. Comparative example 1B, however, did include a CRFM.

The comparative examples were tested for cleanliness. The test used to measure cleanliness is the Volkswagen TDi2 Test. The experimental result is compared against a reference test to determine whether the result is a “pass” or a “fail.” The experimental oil must be better than the reference. The VW TDi2 (CEC L-78-99) is an engine dynamometer test used to measure piston deposits and piston ring sticking of an engine oil. The VW TDi2 uses a Volkswagen 1.9 litre, inline, four-cylinder, turbocharged, direct injection automotive diesel engine. The 54-hour, two-phase test cycle alternates between idle (30 minutes with 40° C. oil sump) and 4150 rpm, full power (150 minutes with 145° C. oil sump). No oil top-ups are allowed during the test. At the conclusion of the 54 hours test, the 4 pistons are removed from the engine and rated for piston cleanliness using a merit scale (higher result is better) and ring sticking. This same test is used for later examples discussed throughout the specification.

In both of the high ash formulations below, the engine oils exhibited a passing TDi2 deposit merit grade. Though it can be seen that comparative example 1B had, even though passing, a lower deposit merit score of 65 as compared with comparative example 1A, which did not include CRFM and exhibited a score of 68.

TABLE 1 Comparative 1A 1B Basestocks Group III Basestock A 37.84 36.36 Group III Basestock B 41 41 Other Includes Antioxidants, 7.28 6.83 Additives Detergents, Antifoams, Pour Point Depressant and Antiwear Viscosity Isoprene-based star polymer 6.55 6.55 Modifier Dispersant Borated Dispersant 3 3 Succinimide Dispersant 4.33 4.33 CRFM Overbased Na Sulfonate Stabilized 1.93 borated friction modifier VW TDi2 Result 68 65 Reference 65 64 Outcome Pass Pass Summary Table CRFM None Detergent Stabilized Dispersant Succinimide, Borated Succinimide, Borated Viscosity Modifier Isoprene-Based Star Isoprene-Based Star Polymer Polymer Cleanliness Booster None None Sulfated Ash 1.20% 1.20%

As noted above, the compositions in Table 1 are “high ash” compositions. Ash, also called “sulfated ash,” is measured by standard test ASTM D874. High ash content leads to plugging of diesel particulate filters which are used as an emission after treatment device on passenger car diesel vehicles. The diesel particulate filter removes particulate matter or soot from the exhaust gas.

A key North American engine oil specification is the dexos1 specification, which specifically requires sulfated ash to be 1.0% in a lubricant formulation. Neither of the formulations here could meet that specification. That is, each of the above comparative examples 1A and 1B have 1.20% sulfated ash. Ash is typically delivered by the detergent system, which provides cleanliness, and the additional ash is capable of cleaning up the deposits that are caused by friction modifiers (especially high concentrations of friction modifiers like CRFM). Comparative example 1A is a formulation without CRFM and the formulation in Comparative example 1B has been balanced for total ash content but contains a CRFM, which is a detergent stabilized CRFM. Detergent stabilized CRFMs have some advantages in that they are typically less expensive and more potent from an active ingredient perspective.

Table 2 below illustrates comparative examples 2A, 2B and 2C. Comparative example 2A is a low ash (i.e., 0.9 wt % sulfated ash) composition that does not include a CRFM. The formulation in comparative example 2A exhibits a passing TDi2 cleanliness score of 65. In each of comparative examples, 2B and 2C, a detergent stabilized CRFM is added to the low ash formulation. As is indicated in Table 2 below, once the CRFM is added to the low ash formulation, the lubricating oil no longer exhibits a passing TDi2 cleanliness score. Indeed, in comparative example 2B the cleanliness score dropped to 54 and in comparative example 2C the cleanliness score dropped to 50.

TABLE 2 Comparative Comparative Comparative 2A 2B 2C Basestocks polyalphaolefin 33.77 33.76 31.45 Group III Basestock A 10 10 10 Group III Basestock B 30 30 30 Ester Co-basestock 5 5 5 Other Additives Includes Antioxidants, Antiwear, 7.66 6.26 7.66 Detergents, Inorganic Friction Modifier and Antifoam Conventional Organic Organic FM 0.52 Friction Modifier Dispersant Borated Dispersant 1.3 1.3 1.3 Succinimide Dispersant 3.25 3.25 polyolefin amide alkeneamine 4.91 dispersant Viscosity Modifier hydrogenated isoprene star 8.5 8.5 7.75 polymer 7 CRFM Overbased Na Sulfonate 1.93 1.93 Stabilized borated friction modifier VW TDi2 Result 65 54 50 Reference 65 65 64 Outcome PASS FAIL FAIL Summary Table CRFM None Detergent Detergent Stabilized Stabilized Dispersant Succinimide, Succinimide, polyolefin amide Borated Borated alkeneamine, Borated Viscosity Modifier Styrene Styrene Styrene Isoprene Isoprene Star Isoprene Star Star Cleanliness Booster None None None Sulfated Ash 0.9% 0.9% 0.9%

A difference between comparative examples 2B and 2C is the dispersant used. In comparative example 2B, the dispersant is a combination of borated and succinimide dispersants. In comparative example 2C, a polyolefin amide alkeneamine dispersant was used instead of the succinimide dispersant. This change in dispersant resulted in further lowering the VW TDi2 score.

Thus, the above indicates that stabilized CRFM systems, like the overbased Na sulfonate stabilized borated friction modifier, are very detrimental to the cleanliness of low ash formulations like comparative example 2A. Comparative examples 2B and 2C contain this ingredient and these formulations resulted in extremely low TDi2 results. These results would lead one skilled in the art to conclude that CRFM could not be used in a low ash formulation that has strong deposit performance.

Table 3 illustrates both comparative (examples 3A, 3F, and 3G) and inventive examples (3B-3E) for additional low ash formulations.

TABLE 3 Comparative Inventive Inventive Inventive Inventive Comparative Comparative Component 3A 3B 3C 3D 3E 3F 3G Basestocks Polyalphaolefin 32.1 31.9 30.6 32.0 31.4 30.7 32.9 Group III Basestock A 10.0 10.0 10.0 10.0 10.0 10.0 29.7 Group III Basestock B 30.0 30.0 30.0 30.0 30.0 30.0 9.9 Ester Co-Basestock 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Other Includes antioxidants, antifoams, antiwear, 8.3 7.1 7.1 7.1 7.1 7.1 7.6 Additives inorganic friction modifiers and detergents Viscosity hydrogenated isoprene star polymer 6 7.6 Modifier hydrogenated isoperene star polymer 7 8.2 5.6 5.0 4.8 1.8 3.5 CRFM Overbased Na Sulfonate Stabilized 1.9 Borated Friction Modifier Ashless Dispersant-Stabilized Borated 3.5 Friction Modifier (Low Stabilizer) Ashless Dispersant-Stabilized Borated 4.0 4.0 4.0 4.0 4.0 Friction Modifier (High Stabilizer) Dispersants Succinimide Dispersant 2.6 6.1 3.2 Borated Dispersant 0.3 1.3 Borated Polyolefin Amide 8.8 Alkeneamine Dispersant Ethylene Capped Succinimide Dispersant 7.4 Succinimide Dispersant 5.4 Polyolefin Amide Alkeneamine Dispersant 9.8 Cleanliness Cleanliness Booster 0.0 1.0 1.0 1.0 1.0 1.0 1.0 Booster VW TDI2 Result 59 65 67 65 66 61 59 Reference 64 65 65 65 65 65 64 Outcome Fail Pass Pass Pass Pass Fail Fail Summary Table Sulfated Ash 0.9% 0.9% 0.9% 0.9% 0.9% 0.9% 0.9%

Comparative example 3A is a low ash formulation including a low stabilizer CRFM. Low stabilizer CRFM obtains the majority of its nitrogen content from the friction modifier portion of the CRFM system. As illustrated above in Table 3, comparative example 3A exhibited a failing TDi2 score of 64. In an effort to improve the TDi2 score, a cleanliness booster was added into comparative examples 3F and 3G. Example 3F included a dispersant stabilized CRFM while example 3G included a detergent stabilized CRFM. A cleanliness booster is known to provide a small benefit on the order of 1-5 merit point credit in the VW TDi2 test and is as described above. Cleanliness boosters typically can provide an incremental but positive benefit, but the effects of cleanliness boosters saturate above approx. 1.5% in composition and are not capable of mitigating significant deposit contributors such as occurs within the broad class of CRFM. Even with the cleanliness booster, comparative examples 3F and 3G each exhibited a failing TDi2 score. Thus, from comparative examples 3F and 3G it can be seen that merely adding a cleanliness booster on its own, whether the formulation includes a CRFM or not, will not improve deposit mitigation in the lubricating oil.

The formulations in inventive examples 3B-3E each include an ashless, dispersant-stabilized, borated CRFM (high stabilizer). Dispersant stabilized CRFM use a borated dispersant as the controlled release agent of the friction modifier. A high stabilizer CRFM is a sub-class of CRFM whereby <50% of the total nitrogen content of the CRFM is derived from the tartrimide. Additionally, the formulations in inventive examples 3B-3E each also include a cleanliness booster. Finally, the formulations in inventive examples 3B-3E each also include a hydrogenated isoprene star polymer 7 viscosity modifier. As can be seen from Table 3 above, each of the inventive examples 3B-3E exhibit a passing TDi2 score in a low ash formulation.

From Table 3, comparative example 3G shows that even if a cleanliness booster is added at 1% with the detergent stabilized CRFM, the formulation still cannot pass the VW TDi2. Furthermore, comparative example 3A shows that merely changing to a dispersant stabilized CRFM alone will not provide a passing TDi2 score.

Instead, the inventive examples 3B-3E in Table 3 provide evidence for the unexpected results that if one combines the cleanliness booster and the dispersant stabilized CRFM with a specific combination of viscosity modifier (hydrogenated isoprene star polymer 7) and one or more of the group of borated succinimide, capped succinimide, succinimide or polyalphaolefin amide alkeneamine dispersant, then one can incorporate a CRFM into a low ash formulation with passing TDi2 results. This result (from inventive examples 3B-3E) was, prior to this application, not only unexpected but also thought to be impossible. That is, conventional thought, prior to the present application, was that a CRFM could not be used in a low ash formulation to obtain a passing TDi2 result.

Table 4 illustrates a preferred example of the lubricating oil composition. Comparative example 4A is a formulation without CRFM and has a very strong TDi2 result of 69. Conventionally, a TDi2 score of 70 is considered an outstanding score. The inventive example in 4B shows that addition of the dispersant stabilized CRFM, in combination with the specific formulation of additives that includes borated succinimide and succinimide dispersants, hydrogenated isoprene star polymer 7 and 1% of cleanliness booster in the low ash formulation shows no impact to cleanliness by adding the CRFM. This is a very surprising and unique result since it is well known that high concentrations of friction modifiers lead to deposits. Indeed, as is illustrated in FIG. 2 and Table 4 below, the formulation in inventive example 4B, with the CRFM added, exhibits the same TDi2 score of 69 as the comparative exampled 4A, without the CRFM.

TABLE 4 Comparative Inventive 4A 4B Basestocks Polyalphaolefin 10 10 Group III Basestock A 53.6 52.2 Group III Basestock B 12 12 Aklylated Naphthalene Co-basestock 5 5 Other Additives Includes antioxidants, antifoams, antiwear, 5.0 5.0 inorganic friction modifiers and detergents Viscosity Modifier Hydrogenated isoprene star polymer 7 6.2 6.4 Cleanliness Booster Cleanliness Booster 0.5 1 Dispersant Borated PIBSA/PAM dispersant 1.2 0.7 Succinimide Dispersant 6 3.7 Conventional Organic Conventional Organic Friction Modifier 0.5 Friction Modifier CRFM Ashless Dispersant-Stabilized Borated 4.0 Friction Modifier (High Stabilizer) VW TDI2 Result 69 69 Reference 65 65 Outcome Pass Pass Summary Table CRFM None Dispersant Stabilized Dispersant Succinimide Borated Succinimide, Succinimide Viscosity Modifier hydrogenated isoprene star hydrogenated isoprene star polymer 7 polymer 7 Cleanliness Booster 0.5% 1.0% Sulfated Ash 0.9% 0.9%

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims. 

What is claimed is:
 1. A lubricant composition, comprising: a lubricating base oil; a controlled release friction modifier including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C₁₈-tartrimide; a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500; a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; a third dispersant; a viscosity modifier; and a cleanliness booster.
 2. The lubricant composition according to claim 1, wherein the viscosity modifier comprises a hydrogenated isoprene star polymer.
 3. The lubricant composition according to claim 1, wherein the cleanliness booster comprises an alkyl phenol ether polymer or polyisobutylene.
 4. The lubricant composition according to claim 1, wherein the third dispersant is selected from a group consisting of succinimide, polyolefin amide alkeneamine, ethylene capped succinimide and borated polyisobutylsuccinimide-polyamine.
 5. The lubricant composition according to claim 1, wherein the lubricating base oil comprises a highly paraffinic base oil.
 6. The lubricant composition according to claim 5, wherein the highly paraffinic base oil includes a polyalphaolefin base oil, a Group III base oil or a combination of the polyalphaolefin base oil and the Group III base oil.
 7. The lubricant composition according to claim 5, wherein the lubricating base oil further comprises a Group V base oil.
 8. The lubricant composition according to claim 1, further comprising a detergent.
 9. The lubricant composition according to claim 8, wherein the detergent is selected from a group consisting of highly overbased calcium salicylate, low base calcium salicylate, overbased magnesium sulfonate and neutral calcium sulfonate.
 10. The lubricant composition according to claim 1, wherein the lubricating base oil comprises between 75% to 90% of the lubricant composition.
 11. The lubricant composition according to claim 1, wherein the dispersant comprises between 1% to 15% of the lubricant composition.
 12. The lubricant composition according to claim 1, wherein viscosity modifier comprises between 1% to 15% of the lubricant composition.
 13. The lubricant composition according to claim 1, wherein the controlled release friction modifier comprises between 2% to 8% of the lubricant composition.
 14. The lubricant composition according to claim 1, wherein the cleanliness booster comprises between 0.5% to 3% of the lubricant composition.
 15. The lubricant composition according to claim 1, wherein the lubricant composition is formulated using a mixture of the controlled release friction modifier and the cleanliness booster, combined into a single homogeneous premix.
 16. A lubricant composition, comprising: 26-94% highly paraffinic base oil; 2%-8% controlled release friction modifier including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C₁₈-tartrimide; a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500; a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; 1%-15% of a third dispersant; 1%-15% viscosity modifier; 1%-10% detergent; and 0.5%-3% cleanliness booster.
 17. A lubricant composition, comprising: a highly paraffinic lubricating base oil; an ashless, dispersant-stabilized, borated controlled release friction modifier including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C₁₈-tartrimide; a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500; a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; a third dispersant selected from a group consisting of succinimide, polyolefin amide alkeneamine, ethylene capped succinimide and borated polyisobutylsuccinimide-polyamine; a viscosity modifier comprising a hydrogenated isoprene star polymer; and a cleanliness booster comprising an alkyl phenol ether polymer or polyisobutylene.
 18. A lubricant composition, consisting of: 10% polyalphaolefin base oil; 64.21% Group III base oil; 5% alkylated naphthalene co-baseoil; 4.99% of supporting additives including antioxidants, detergents, antiwear, antifoam, inorganic friction modifiers and pour point depressants; 6.4% hydrogenated isoprene star polymer 7; 1% of a cleanliness booster; 0.74% borated PIBSA/PAM dispersant; 3.96% of an ashless, dispersant-stabilized borated friction modifier Including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C₁₈-tartrimide; a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500; a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; and 3.7% of a succinimide dispersant differing from either the first dispersant and second dispersant. 